1. Field of Disclosure
The present disclosure of invention relates to a hand piece. More particularly, the present disclosure of invention relates to a hand piece used for a medical treatment.
2. Description of Related Technology
Generally, in an air-driven hand piece used for a medical treatment, a pressurized air is provided to an impeller received by a head of the hand piece and thus a cutting tool fixed at the impeller is rotated.
In the hand piece, an air flow due to the rotation of the impeller generates pressure difference between an inside of the head and an outside of the head, and this a sound pressure is generated in the head whenever the pressurized air stops being provided. Here, foreign substance or impurities may be inhaled into the head through a gap between the head and the cutting tool, and it is called as “Suck Back”.
The impurities may be stacked in the hand piece due to the Suck Back, and the impurities may be exposed to the patient so that the patient may be infected by the hand piece. Thus, various kinds of hand pieces have been developed to prevent the Suck Back. However, the head of the hand piece is limited in the space and the structure, and thus the hand piece for preventing the Suck Back is hard to be designed within the head of the hand piece.